ZDoom

I'd like some ZScript functions to dynamically swap out the current model and also skin (AKA texture) during runtime. Yes, I am aware that currently the resources are loaded at startup... I'm kindly requesting it to be possible for these resources to be swapped out during runtime.

No. The model links are per-class, not per-actor. Changing this at run-time would not only put some significant drag on the actor but also require saving of all that baggage.